HeterochiralD NA with hydrogen-bondedand silver-mediated base pairs have been constructed using complementary strandsw ith nucleosides with ad or b-d configuration. Anomeric phosphoramidites were employed to assemble the oligonucleotides. According to the T m values and thermodynamic data, the duplex stabilityo ft he heterochiral duplexes was similart ot hat of homochiral DNA, but mismatch discrimination was better in heterochiral DNA. Replacement of purinesb y7-deazapurines resulted in stable paralleld uplexes, thereby confirming Watson-Crick-type base pairing. When cytosine wasf acing cytosine, thymine or adenine residues, duplex DNA formed silver-mediated base pairs in the presence of silver ions. Although the CD spectra of single strands with ad configuration display mirror-like shapes to those with the b-d configuration, the CD spectra of the hydrogen-bonded duplexes and those with al imited number of silver pairs show aB-type double helix almost indistinguishable from naturalD NA. Nonmelting silver ion-DNA complexesw ith entirely different CD spectra were generatedwhen the number of silver ions was equalt ot he number of base pairs.